I have never seen any plastic soda or water bottle do anything more than soften up when boiling water is put inside.
As for boiling, well the lowest altitude of the places i have used this trick would be the Sierra Nevada (about 9,000), the Cascades (6,000 or so) and the San Juans of Colorado (Also 9 to 11,000).
The hot water bottle trick is , as you would expect, mostly a high altitude/cold temperature thing.
So I suppose the boiling temperature was less than 212 degrees Farenheit.
So around 170 degree water was what i was using at that altitude.
Perhaps at sea level there could be an issue with true 212 degree water in a cheap plastic soda/water bottle.
The again, never need to use the trick at those altitudes.
Either way I can say that I have never had a failure nor have any of my long distance hiker buddies spoken of a failure of a soda bottle treated in this way.
I am sure there is one person out there that has had a failure, but i never met them.
Make sure the cap is tight.
Replace the bottle occasionally.
Thats the best advice i have.